Certain state of the art gas turbine engines, as the TF-30 manufactured by Pratt & Whitney Aircraft Group of United Technologies Corporation, the assignee of this patent application, utilize Finwall.RTM. material as the basic materials for fabricating the liner wall. For further details of Finwall material reference should be made to the TF-30 engine, supra, and U.S. Pat. No. 3,706,203 granted to P. Goldberg and I. Segalman on Dec. 19, 1972. For the purpose of this description, suffice it to say that Finwall material comprises a pair of spaced walls formed in cylindrical bodies and attached end over end in louver fashion to form the combustion chamber. Either parallel depending walls extending in a gratelike fashion from one wall interconnect the other wall and define therewith a plurality of open-ended longitudinal passageways. Because of the louver construction, the upstream end accepts cooling air from the surrounding space and discharges it from the passageways at the downstream end into the combustion chamber. Succeeding louver sections pick up and discharge the cooling air in a like manner.
The above cross-referenced patent application modifies the Finwall constructed liner, by providing inlet openings intermediate the ends of the Finwall material and conducts the cooling air in a counter and parallel flow relation to the combustion products. This not only serves to improve the temperature gradient along the longitudinal and radial directions it permits spacing the segments inasmuch as the discharge cooling air film cools the transition zones.
I have found that I can not only take advantage of the cooling features mentioned above, but I can obtain even extended liner life by not attaching the hotter liner wall member to the cooler one thereby allowing it to float. Further cooling is obtained by extending the downstream end of the floating wall to define a lip and thereby reestablishes a film of cooling air for improved film cooling of the transition section. It is contemplated within the scope of this invention that the hot liner wall is segmented in both the axial and circumferential direction. The axial segments are sufficiently spaced whereby film cooling provides adequate cooling between axial segments and the space between segments in the circumferential direction permits circumferential growth. The circumferential growth negates the possibility of radial growth and minimizes detrimental thermal stress and leaves the cooling flow passages relatively undisturbed. Each segment may be secured relative to the cool wall by a nut and bolt arrangement designed to achieve minimum stresses.